234 



METALLIC SULPHIDES. 



Proto-sulphide of iron. 



Proto-sulphide of manganese. 



Proto-snlphide of zinc. (Zinc blende.) 



Proto-sulpliide of cadmium. 



Proto-sulphide of tin. 



Proto-sulphide of mercury. (Cinnabar.) 



Proto-sulphide of silver. 



Proto-sulphide of lead. (Galena.) 



Sub-sulphide of copper. 



Sulphide of copper and iron. (Copper pyrites.) 



Bi-sulphide of iron. (Iron pyrites.) 



Sulphide of antimony. (Stibnite.) 



Sulj)hide of gold. 



Sulphide of platinum. 



Sulpho-arsenide of iron. (Mispickel.) 



Carbon, as graphite, sulphurized. 

 Compared with some of the metals, it was ascertained that in the same 

 kind of solution zinc is positive to proto-sulphide of iron, while silver places 

 itself between sulphide of silver and galena, and platinum between sulphide of 

 platina and mispickel ; graphite (freshly ignited) being negative to the whole 

 of this series. 



In weak sulphuric acid, the electro-motive order of these stilphides appears 

 the same as in saline solutions, at least this was shown to be the case for the 

 following : — proto-sulphide of iron^ sub-sulphide of copper, zinc blende, galena, 

 copper pyrites, and cubic iron pyrites. The greater number of these sulphides 

 were natural productions. 



Magnetite was found to be negative to galena, but positive to mispickel in 

 saline solutions ; hematite is generally negative to these suli:)hides, but its 

 very inferior conducting power renders it difficult to obtain results with it. 



Some of these minerals are so weakly positive to the one immediately 

 below them, that slight admixtures with them of other siilphides might, very 

 likely, change their positions in this column. Sulphide of antimony and mis- 

 pickel, for instance, form a very weak voltaic pair, in which were a minute 

 quantity of another sulphide to enter on either side, their position as here 

 tabulated might be reversed. 



A ciirious fact is expressed in this column, viz., that galena is more easily 

 affected by these decomposing agents than cojiper pyrites ; this being the 

 opposite of what I should have supposed, as galena appears unalterable in 

 ordinary circumstances, while the copper pyi-ites very soon discolours. 



Compared to magnetite or hematite, the siilphides generally are far superior 

 conductors of electricity. 



